What happened
On March 12, 1969, at approximately 10:17 AM, an Agusta Bell 206 A Jet Ranger, registration HB-XCL, was performing a flight from Zermatt to the Upper Theodul Glacier. The mission involved transporting passengers to various high-altitude ski areas.
As the pilot approached a landing site near the end of the Trockener Steg/Furggs and station, the terrain was covered in snow under diffuse lighting conditions. While attempting to hover and find a suitable spot, the aircraft unexpectedly made contact with the ground. The right skid became lodged in the soft snow, causing the helicopter to tilt sideways and lose control. Although a small fire broke out near the turbine exhaust, the pilot was able to extinguish it using the onboard fire extinguisher. All three occupants (the pilot and two passengers) escaped the cabin without injury.
The investigation
Investigators examined the aircraft, the pilot's credentials, and the environmental conditions at the time of the accident. The HB-XCL was found to be properly maintained, with its last 100-hour inspection completed recently, and no mechanical defects were identified. The pilot held a valid commercial license with specific endorsements for mountain and night flying and was highly familiar with both the aircraft type and the local terrain.
Weather observations at the crash site revealed 8/8 cloud cover at approximately 3,550 meters, with visibility between 1 and 3 kilometers and light blowing snow. The temperature was -10°C. The investigation also noted that while the landing site was an authorized area for tourist landings, the lack of visual landmarks made the approach difficult.
Findings
- The primary cause of the accident was that the pilot failed to recognize the ground in time due to diffuse lighting which rendered the snow surface without contrast.
- The pilot was flying with a lateral drift rather than straight ahead because the lack of visual references on the snow prevented a stable approach.
- The nearby ski lift infrastructure was too far from the landing path to serve as a useful visual reference point under the prevailing conditions.
- The light and visibility conditions were objectively insufficient for performing an external landing on an unmarked site.